I was wondering about the fitting of the computer transponder/ receiver on the fork leg/ wheel.
I have set the computer to the 26 inch wheel as setup advised but should the transponder/receiver be at a certain height on the leg and as far out to the outside rim of the wheel or does the computer allow for a fitting more central to the hub.
The computer works none the less.
But yesterday swmbo's computer and mine showed different readings whilst we were out riding.

The magnet only passes the sensor once on each revolution – it doesn't matter whether the magnet is close to the hub or far away. The reason why your getting different readings is because one or both of you have the wrong set up. The guide in the manual gets you close – if you want it to be accurate you need to ride forwards, say, 10 wheel revolutions and then divide the distance by 10 to get the circumference of the wheel.

What aP said.

The wheel-diameter calibration settings are often inaccurate. You need to find a known distance.

eg. there's a straight section of road locally which Google maps tells me is exactly 2.55km between junctions, so I ride that road and then adjust the "wheel circumference" setting by a factor of (actual distance) / (recorded distance).

What about marking a spot on the tire and again on a flat surface then rolling forward one full wheel rotation then measuring the distance in millimeters and putting that setting into the computer.
Its going to be pretty close give or take a mill or two
I can do that with my computer but swmbo's is less advanced.